BR112014017195B1 - PEROXIDE-FREE RETICULABLE THERMOPLASTIC COMPOSITION, PROCESS TO PREPARE A RETICULATED SEMICONDUCTOR THERMOPLASTIC ARTICLE, IN-LINE PROCESS TO PREPARE A RETICULABLE COMPOSITION AND GRAIN - Google Patents

Abstract

peroxide-free semiconductor crosslinkable thermoplastic composition, process for preparing a crosslinked semiconductor thermoplastic article, in-line and granule process. peroxide-free semiconductor crosslinkable thermoplastic compositions having a stable volumetric resistivity of less than 1000 ohm-cm comprising, based on the weight of the composition: a. 60-90% by weight of silane-functionalized polyethylene; B. from 0.5-20% by weight of organopolysiloxane containing two or more functional terminal groups; w. of 10-20% by weight of high conductivity carbon black, such as a carbon black having an average particle size of 50 nm or less, a surface area (bet) of 700-1250 m2/g and an absorption of oil (dbp) of 300-500 ml/100 g; and d. from 0.05 - 0.2% by weight of crosslinking catalyst.

Description

technical field

[001] In one aspect, the invention relates to crosslinkable semiconductor thermoplastic compositions, while in another aspect, the invention relates to the use of these compositions in a process to prepare crosslinked semiconductor articles under ambient conditions and without the use of peroxides.

prior technique

[002] Existing technologies for manufacturing crosslinked articles from thermoplastic compositions are mainly based on peroxide-based compounds. Depending on whether the article under manufacture is molded or extruded, the manufacturing methods differ from each other. For example, for a molded article, typically crosslinkable thermoplastic compositions are first molded into a tape or strip, fed into a rubber injection press for melt molding, and finally cured in a hot mold at about 175°C for 5 to 15 minutes (depending, among other things, on composition formulation and article thickness). For an extruded cable, crosslinkable thermoplastic compositions are fed into an extruder and coextruded along with the insulating compound into a metallic conductor, and then passed through a continuous high temperature vulcanization (CV) tube to induce crosslinking. In either case, the peroxide cure initiator can be pre-incorporated or combined with the crosslinkable thermoplastic composition at any point in the process. Pre-vulcanization (“scorch”), that is, premature reticulation, is a common problem with this technology.

[003] In the manufacture of cables, the process is slow, mainly driven by the limitation in obtaining adequate cure through the entire thickness of the cable, especially in the internal semiconductor sheath. Another technology used in the manufacture of cables is based on moisture curing, in which the cable is immersed in hot water or a sauna (steam bath) to induce crosslinking. In this case, there is a serious limitation in the diffusion of moisture to the innermost layer of the cable, that is, in the conductor sheath, which consequently requires long curing times. Thus, there are limitations of current moisture curing techniques with respect to reduced size cables.

Invention Summary

[004] In one embodiment, the invention is a semiconductor, peroxide-free crosslinkable thermoplastic composition, having a stable volumetric resistivity of less than 1000 ohm-cm at 90°C, comprising, based on the weight of the composition:

[005] A. from 60-90% by weight of silane-functionalized polyethylene;

[006] B. from 0.5-20% by weight of organopolysiloxane containing two or more functional end groups;

[007] C. of 10-20% by weight carbon black; and

[008] D. from 0.05 - 0.2% by weight of crosslinking catalyst.

[009] In one embodiment, the invention is a process for preparing a crosslinked semiconductor thermoplastic article, having a stable volumetric resistivity of less than 1000 ohm-cm at 90°C, the process comprising the steps of:

[010] A. Combining a silane-functionalized polyethylene with an organopolysiloxane containing two or more functional end groups to form a crosslinkable compound;

[011] B. combining under ambient conditions (1) the crosslinkable compound of (A) with (2) carbon black to form a first mixture comprising from 80-90% by weight of the crosslinkable compound of (A) and 10-20 % by weight of carbon black, based on the weight of the first mixture;

[012] C. combine the first mixture with 0.05-0.2% by weight of a crosslinking catalyst to form a second homogeneous mixture;

[013] D. molding the second mixture under non-crosslinking conditions, into a crosslinkable semiconductor thermoplastic article; and

[014] E. subjecting the molded crosslinkable semiconductor thermoplastic article to crosslinking conditions.

[015] In one embodiment, the process comprises the additional steps of (a) preparing the silane-functionalized polyethylene, grafting a polyethylene with a silane compound under grafting conditions, and (b) pelletizing the crosslinkable compound from (A) before of mixing it with the organopolysiloxane. In one embodiment, the process comprises the additional steps of (a) preparing the silane-functionalized polyethylene by copolymerizing ethylene with a vinyl silane under copolymerization conditions, and (b) pelletizing the crosslinkable compound of (A) before mixing it with the organopolysiloxane.

[016] In one embodiment, the process comprises the steps of (a) preparing a silane-functionalized polyethylene, grafting a polyethylene with a silane compound under grafting conditions; (b) mixing the silane-functionalized polyethylene with an organopolysiloxane; (c) mixing the conductive charge (filler) (a), such as a carbon black, with the mixture formed in step (b) and (d) recovering and pelletizing the mixture formed in step (c). All steps are carried out in a single container, ie the process is an in-line process.

[017] In one embodiment, the invention is a pellet free of crosslinking catalyst, the pellet comprising:

[018] A. from 60-90% by weight of silane-functionalized polyethylene;

[019] B. from 0.5-20% by weight of organopolysiloxane containing two or more functional end groups; and

[020] C. of 10-20% by weight of high conductivity carbon black.

[021] Free from crosslinking catalyst means that a catalyst, capable of crosslinking the granule composition under process conditions, such as 23°C and atmospheric pressure, is not added at any stage of the process.

Detailed Description of Preferred Embodiment Definitions

[022] The numerical ranges in this report are approximate and may include values outside the range, unless otherwise indicated. Numeric ranges include all values from and including the minimum and maximum values, in increments of one unit, provided there is a gap of at least two units between any minimum value and any maximum value. As an example, if a compositional, physical or other property, such as, for example, molecular weight, viscosity, melt index, etc., is from 100 to 1,000, it is intended that all individual values, such as 100, 101, 102, etc., and subranges such as 100 to 144, 155 to 170, 197 to 200, etc., are expressly enumerated. For ranges containing values less than one or containing fractional numbers greater than one (eg 1.1, 1.5, etc.), a unit will be considered as 0.0001, 0.001, 0.01, or 0.1, as appropriate . For ranges containing single-digit numbers less than ten (eg, 1 to 5), a unit is typically considered to be 0.1. These are just examples of what is specifically intended, and all possible combinations of numerical values between the lowest and highest enumerated values should be considered as expressly cited in this report. Numerical ranges are provided in this report, among other things, composition component amounts and various process parameters.

[023] "Cable" and similar terms mean at least one wire or optical fiber within a protective insulation, jacket or sheath. Typically, a cable consists of two or more wires or optical fibers bonded together, typically in a common insulation, jacket, or protective sheath. The individual strands or fibers within the jacket can be bare, capped or insulated. Combined cables can contain both electrical wires and optical fibers. Cable etc. can be designed for low, medium and high voltage applications. Typical cable designs are illustrated in US Patent Nos. 5,246,783, 6,496,629 and 6,714,707.

[024] "Polymer" means a compound prepared by reacting (ie polymerizing) monomers, of the same or different type. The generic term polymer thus encompasses the term "homopolymer", generally used to refer to polymers prepared with only one type of monomer, and the term "interpolymer", as defined below.

[025] "Interpolymer" and "copolymer" mean a polymer prepared by polymerizing at least two different types of monomers. These generic terms include both classical copolymers, that is, polymers prepared with two different types of polymers, and polymers prepared with two different types of monomers, such as, for example, terpolymers, tetrapolymers, etc.

[026] "Ethylene polymer", "polyethylene" and similar terms mean a polymer containing units derived from ethylene. Ethylene polymers typically comprise at least 50 mole percent (mol %) of ethylene-derived units.

[027] "Ethylene-vinylsilane polymer" and similar terms mean an ethylene polymer comprising silane functionality. The silane functionality can be the result of polymerizing ethylene with a vinyl silane, for example, a trialkoxy silane comonomer, or grafting such a comonomer with an ethylene polymer backbone, as described, for example, in USP 3,646 .155 or 6,048,935.

[028] “Blenda”, “polymer blend” and similar terms mean a blend of two or more polymers. This blend may or may not be miscible. Such a blend may or may not be separated into phases. Such a blend may or may not contain one or more domain configurations, as determined by transmission electron microscopy, light scattering, X-ray scattering, and any other method known in the prior art.

[029] “Composition” and similar terms mean a mixture or blend of two or more components. For example, in the context of preparing a silane grafted ethylene polymer, a composition would include at least one ethylene polymer, at least one vinyl silane and at least one free radical initiator. In the context of preparing a cable sheath or other article of manufacture, a composition would include an ethylene-vinylsilane copolymer, a catalytic cure system, and any desired additives, such as lubricants, fillers, antioxidants, and the like.

[030] “Ambient conditions” and similar terms mean the temperature, pressure and humidity of the area or environment surrounding an article. The environmental conditions of a typical laboratory or production facility include a temperature of 23°C and atmospheric pressure.

[031] "Catalytic amount" means an amount of catalyst necessary to promote the crosslinking of an ethylene-vinylsilane polymer at a detectable level, preferably at a commercially acceptable level.

[032] "Reticulated", "cured" and similar terms mean that the polymer, before or after being molded into an article, has been subjected or exposed to a treatment that induced crosslinking and that it has extractables of xylene or dekalene in an equal amount or less than 90 percent by weight (i.e., equal to or greater than 10 percent by weight gel content).

[033] "Cross-linkable", "curable" and similar terms mean that the polymer, before or after being cast into an article, is not cured or cross-linked and has not been subjected to or exposed to treatment that has induced substantial cross-linking, although the polymer comprises additive(s) or functionality that will cause or promote substantial crosslinking when subjected to or exposed to such treatment (eg, exposure to water).

[034] "Mold-formed" and similar terms refer to an article prepared with a thermoplastic composition that has acquired a configuration as a result of processing in a mold or through a die while in a molten state. The molten shaped article may be at least partially cross-linked to maintain the integrity of its configuration. Fusion configured articles include wire and cable sheaths, parts, plates, tapes, strips and the like, molded by compression or injection.

[035] "Peroxide free" and similar terms mean that the amount of peroxide present in the crosslinkable, semiconductor and thermoplastic compositions and articles of the present invention does not exceed the amount, if any, of residual peroxide remaining from grafting a silane functionality onto the polyethylene . Typically, this amount is less than 300 parts per million (ppm), preferably less than 100 ppm. Except for grafting silane functionality onto polyethylene, peroxide is not added to the compositions and articles of the present invention.

[036] "Stable volumetric resistivity" and similar terms mean a volumetric resistivity in ohm-cm of a composition or crosslinked article that does not change by more than 30%, preferably by more than 20% and even more preferably by more than 10% , after an oven aging period of 15 days at 90°C.

[037] “Pellet” and similar terms mean small particles typically created by compressing a powder or granular material, or cutting filaments created during the extrusion of a melt through a die. Bead shapes and sizes can vary widely. Ethylene Polymers

[038] The polyethylenes used in the practice of the present invention, that is, the polyethylenes containing copolymerized silane functionality or that are later grafted with a silane, can be produced using conventional polyethylene polymerization technology, such as, for example, high catalysis pressure, Ziegler Natta, metallocene or constrained geometry. In one embodiment, polyethylene is prepared using a high pressure process. In another embodiment, polyethylene is prepared using a transition metal (preferably Group 4) mono- or bis-cyclopentadienyl, indenyl, or fluorenyl catalysts or catalysts in combination with an activator, in a polymerization process in solution, paste or gas phase. The catalyst is preferably monocyclopentadienyl, monoindenyl or monofluorenyl CGC. The solution process is preferred. USP patents 5,064,802, WO93/19104 and WO95/00526 describe metal complexes of constrained geometry and methods for their preparation. Variously substituted indenyl-containing metal complexes are described in WO95/14024 and WO98/49212.

[039] In general, the polymerization can be carried out under conditions well known in the state of the art for Ziegler-Natta or Kaminsky-Sinn polymerization reactions, that is, at temperatures from 0-250°C, preferably from 30-200°C and pressures ranging from atmospheric to 10,000 atmospheres (1013 megaPascal (MPa)). Polymerization in suspension, solution, paste, gas phase, solid state powder or other process conditions may be employed, if desired. The catalyst can be supported or unsupported, and the composition of the support can vary widely. Silica, alumina or a polymer (especially poly(tetrafluoroethylene) or a polyolefin) are representative supports, and desirably a support is employed when the catalyst is used in a gas phase polymerization process. The support is preferably employed in an amount sufficient to provide a weight ratio of catalyst (metal based) to the support in a range of from 1:100,000 to 1:10, more preferably from 1:50,000 to 1:20 and most preferably from 1:10,000 to 1:30. In most polymerization reactions, the molar ratio of catalyst to polymerizable compounds employed is from 10-12:1 to 10-1:1, more preferably from 10-9:1 to 10-5:1.

[040] Inert liquids serve as suitable solvents for polymerization. Examples include straight and branched chain hydrocarbons such as isobutane, butane, pentane, hexane, heptane, octane and mixtures thereof; cyclic and alicyclic hydrocarbons, such as cyclohexane, cycloheptane, methylcyclohexane, methylcycloheptane, and mixtures thereof; perfluorinated hydrocarbons such as perfluorinated C4-10 alkanes; and alkyl substituted aromatic and aromatic compounds such as benzene, toluene, xylene and ethylbenzene.

[041] Ethylene polymers useful in the practice of the present invention include ethylene/α-olefin interpolymers having an α-olefin content of at least 15, preferably of at least 20 and even more preferably of at least 25% by weight, with based on the weight of the interpolymer. Such interpolymers typically have an α-olefin content of less than 50, preferably less than 45, more preferably less than 40 and even more preferably less than 35 percent by weight, based on the weight of the interpolymer. α-Olefin content is measured by 13 C nuclear magnetic resonance spectroscopy using the procedure described in Randall (Rev. Macromol. Chem. Phys., C29 (2&3)). Generally, the higher the α-olefin content of the interpolymer, the lower the density and the more amorphous the interpolymer, which translates into desirable physical and chemical properties for the protective insulating layer.

[042] The α-olefin is preferably a linear, branched or cyclic C3-20 α-olefin. Examples of C3-20 α-olefins include propene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-octadecene . α-olefins can also contain a cyclic structure, such as cyclohexane or cyclopentane, resulting in an α-olefin, such as 3-cyclohexyl-1-propene (allyl cyclohexane) and vinyl cyclohexane. While not α-olefins in the classical sense of the term, for the purposes of the present invention, certain cyclic olefins, such as norbornene and related olefins, particularly 5-ethylidene-2-norbornene, are α-olefins and may be used in place of some or all of the α-olefins described above. Similarly, styrene and its related olefins (e.g., α-methylstyrene, etc.) are α-olefins for purposes of the present invention. Illustrative ethylene polymers include ethylene/propylene, ethylene/butene, ethylene/1-hexene, ethylene/1-octene, ethylene/styrene and the like. Illustrative terpolymers include ethylene/propylene/1-octene, ethylene/propylene/butene, ethylene/butene/1-octene, ethylene/propylene/diene monomer (EPDM) and ethylene/butene/styrene. Copolymers can be random or block.

[043] The ethylene polymers used in the practice of the present invention can be used alone or in combination with one or more other ethylene polymers, such as a blend of two or more ethylene polymers that differ in relation to composition and monomer content, catalytic method of preparation, etc. If the ethylene polymer is a blend of two or more ethylene polymers, then the ethylene polymer can be blended through any in-reactor or post-reactor process. In-reactor mixing processes are preferred over post-reactor mixing processes, and processes using multiple reactors connected in series are preferred in-reactor mixing processes. These reactors can be loaded with the same catalyst, although operated under different conditions, such as reactant concentrations, temperatures, pressures, etc. different, or operated under the same conditions, though loaded with different catalysts.

[044] Examples of ethylene polymers prepared with high pressure processes include (but are not limited to) low density polyethylene (LDPE), ethylene silane reactor copolymer (such as SiLINK® prepared by The Dow Chemical Company), copolymer of ethylene vinyl acetate (EVA), ethylene ethyl acrylate copolymer (EEA) and ethylene silane acrylate terpolymers.

[045] Examples of ethylene polymers that can be grafted with silane functionality include very low density polyethylene (VLDPE) (eg FLEXOMER® ethylene/1-hexene polyethylene prepared by The Dow Chemical Company), ethylene/α-copolymers linear, homogeneously branched olefin polymers (eg, TAFMER® from Mitsui Petrochemicals Company Limited and EXACT® from Exxon Chemical Company), homogeneously branched, substantially linear ethylene/α-olefin polymers (eg, polyethylene AFFINITY® and ENGAGE® from The Dow Chemical Company ) and ethylene block copolymers (eg INFUSE® polyethylene from The Dow Chemical Company). The most preferred ethylene polymers are substantially linear homogeneously branched ethylene copolymers. Substantially linear ethylene copolymers are especially preferred, and more broadly described in USP 5,272,236, 5,278,272 and 5,986,028.

Silane functionality

onde R1 é um átomo de hidrogênio ou grupo metila; x e y são 0 ou 1 com a condição de que quando x for 1, y seja 1; m e n são independentemente um número inteiro de 0 a 12 inclusive, preferivelmente de 0 a 4, e cada R” é independentemente um grupo orgânico hidrolisável, tal como um grupo alcoxi tendo de 1 a 12 átomos de carbono (ex: metoxi, etoxi, butoxi), grupo ariloxi (ex: fenoxi), grupo araloxi (ex: benziloxi), grupo aciloxi alifático tendo de 1 a 12 átomos de carbono (ex: formiloxi, acetiloxi, propanoiloxi), grupos amino ou substituídos com amino (alquilamino, arilamino), ou um grupo alquila inferior tendo de 1 a 6 átomos de carbono inclusive, contanto que não mais que um dos três grupos R seja um alquila. Tais silanos podem ser copolimerizados com etileno em um reator, tal como um processo de alta pressão. Tais silanos podem também ser enxertados a um polímero de etileno apropriado mediante o uso de uma quantidade apropriada de peróxido orgânico, seja antes ou durante uma operação de configuração ou moldagem. Ingredientes adicionais, tais como estabilizantes térmicos e de luz, pigmentos, etc. também podem ser incluídos na formulação. A fase do processo durante o qual as retículas são criadas é comumente designada como “fase de cura” e o próprio processo é comumente designado como “cura”. São também incluídos os silanos adicionados à insaturação no polímero via processos de radical livre, tal como o mercaptopropil trialcoxisilano.[046] Any silane that effectively copolymerizes with ethylene or that can be grafted to and cross-linked with an ethylene polymer, can be used in the practice of the present invention, as well as those described by the following formula, are representative:

where R1 is a hydrogen atom or methyl group; x and y are 0 or 1 with the proviso that when x is 1, y is 1; men are independently an integer from 0 to 12 inclusive, preferably from 0 to 4, and each R" is independently a hydrolyzable organic group, such as an alkoxy group having 1 to 12 carbon atoms (eg methoxy, ethoxy, butoxy ), aryloxy group (eg phenoxy), araloxy group (eg benzyloxy), aliphatic acyloxy group having 1 to 12 carbon atoms (eg formyloxy, acetyloxy, propanoyloxy), amino or substituted amino groups (alkylamino, arylamino) , or a lower alkyl group having from 1 to 6 carbon atoms inclusive, provided that no more than one of the three R groups is an alkyl. Such silanes can be copolymerized with ethylene in a reactor, such as a high pressure process. Such silanes can also be grafted to a suitable ethylene polymer using an appropriate amount of organic peroxide, either before or during a shaping or molding operation. Additional ingredients such as heat and light stabilizers, pigments, etc. can also be included in the formulation. The phase of the process during which the reticles are created is commonly referred to as the “cure phase” and the process itself is commonly referred to as the “cure”. Also included are silanes added to unsaturation in the polymer via free radical processes, such as mercaptopropyl trialkoxysilane.

[047] Suitable silanes include unsaturated silanes comprising ethylenically unsaturated hydrocarbyl group, such as a vinyl, allyl, isopropenyl, butenyl, cyclohexenyl or gamma-(meth)acryloxyallyl group, and a hydrolyzable group such as, for example, a group hydrocarbyloxy, hydrocarbonyloxy, or hydrocarbylamino. Examples of hydrolyzable groups include methoxy, ethoxy, formyloxy, acetoxy, propionyloxy, and alkyl or arylamino groups. Preferred silanes are unsaturated alkoxy silanes which can be grafted onto the polymer or reactor copolymerized with other monomers (such as ethylene and acrylates). These silanes and their method of preparation are more fully described in USP 5,266,627 of Meverden, et al. Vinyl trimethoxy silane (VTMS), vinyl triethoxy silane, vinyl triacetoxy silane, gamma-(meth)acryloxy propyl trimethoxy silane, and mixtures of these silanes are the preferred silane crosslinkers for use in the present invention. If the charge is present, then preferably the cross-linker includes vinyl trialkoxy silane.

[048] The amount of silane crosslinker used in the practice of the present invention can vary widely depending on the nature of the polymer, silane, processing or reactor conditions, grafting or copolymerization efficiency, end application, and factors similar, although typically at least 0.5, preferably at least 0.7 percent by weight is used. Convenience and economic considerations are two of the major restrictions on the maximum amount of silane crosslinker used in the practice of the present invention, and typically the maximum amount of silane crosslinker does not exceed 5, preferably does not exceed 3 percent by weight.

[049] The silane crosslinker is grafted to the polymer through any conventional method, typically in the presence of a free radical initiator, for example, peroxides and azo compounds, or through ionizing radiation, etc. Organic initiators are preferred, as are any of the peroxide initiators, for example, dicumyl peroxide, di-tert-butyl peroxide, t-butyl perbenzoate, benzoyl peroxide, cumene hydroperoxide, t-butyl peroctoate, peroxide of methyl ethyl ketone, 2,5-dimethyl-2,5-di(t-butyl peroxy) hexane, lauryl peroxide, and tert-butyl peracetate. A suitable azo compound is 2,2-azobisisobutyronitrile. The amount of initiator may vary, although it is typically present in an amount of at least 0.01, preferably at least 0.03 part per hundred parts of resin (phr). Typically, the initiator does not go beyond 0.15, preferably does not go beyond about 0.10 phr. The weight ratio of silane to initiator crosslinker can also vary widely, although the typical crosslinker:initiator weight ratio is between 10:1 to 500:1, preferably between 18:1 and 250:1. As used, in parts per hundred parts of resin or phr, "resin" means the olefinic polymer.

[050] Although any conventional method can be used to graft the silane crosslinker to the polyolefin polymer, a preferred method is to mix the two with the initiator in the first stage of an extruder reactor, such as the Buss kneader. Grafting conditions can vary, although melting temperatures are typically between 160 and 260°C, preferably between 190 and 230°C, depending on the residence time and half-life of the initiator.

[051] The copolymerization of vinyl trialkoxysilane crosslinkers with ethylene and other monomers can be carried out in a high pressure reactor that is used in the manufacture of homopolymers and copolymers of ethylene with vinyl acetate and acrylates.

Polyfunctional Organopolysiloxane with Functional End Groups

[052] Oligomers containing functional end groups useful in the process of the present invention comprise from 2 to 100,000 or more units of the formula R2SiO where each R is independently selected from a group consisting of alkyl radicals comprising from one to 12 carbon atoms, alkenyl radicals comprising from two to 12 carbon atoms, aryl, and fluorine-substituted alkyl radicals comprising from one to 12 carbon atoms. The radical R can be, for example, methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, dodecyl, vinyl, allyl, phenyl, naphthyl, tolyl and 3,3,3-trifluoropropyl. It is preferred when each R radical is methyl.

[053] In one embodiment, the organopolysiloxane containing one or more functional end groups is a hydroxyl-terminated polydimethylsiloxane containing at least two hydroxyl end groups. Such polydimethylsiloxanes are commercially available, for example, as silanol terminated polydimethylsiloxane from Gelest, Inc. However, polydimethylsiloxanes containing other end groups which can react with grafted silanes, for example, amine-terminal polydimethylsiloxanes and the like can be used . In preferred embodiments, the polydimethylsiloxane has the formula:

[054] where Me is methyl and n is in the range of 2 to 100,000 or more, preferably in the range of 10 to 400, and more preferably in the range of 20 to 120. Examples of suitable polyfunctional organopolysiloxanes are silanol terminated polydimethylsiloxane DMS-15 (Mn 2,000-3,500, viscosity 45-85 centistokes, -OH level 0.9-1.2%) from Gelest Corp., and Silanol Fluid 1-3563 (viscosity 55-90 centistokes, -OH level 1 -1.7%) of Dow Corning Corp. In some embodiments, the polyfunctional organopolysiloxane comprises branches such as those imparted by the Me-SiO3/2 or SiO4/2 groups (known as Tor Q groups to those skilled in silicone chemistry).

[055] The amount of organopolysiloxane used in the practice of the present invention can vary widely depending on the nature of the polymer, silane, polyfunctional organopolysiloxane, processing and reactor conditions, end application and similar factors, but typically at least 0.5, preferably at least 2 percent by weight is used. Convenience and economic considerations are two of the main restrictions on the maximum amount of polyfunctional organopolysiloxane used in the practice of the present invention, and typically the maximum amount of polyfunctional organopolysiloxane does not exceed 20, preferably does not exceed 10 percent by weight. Catalyst

[056] Useful crosslinking catalysts include Lewis and Bronsted acids and bases. Lewis acids are chemical species that can accept an electron pair from a Lewis base. Lewis bases are chemical species that can donate a pair of electrons to a Lewis acid. Lewis acids which may be used in the practice of the invention include tin carboxylates such as dibutyl tin dilaurate (DBTDL), dimethyl hydroxy tin oleate, dioctyl tin maleate, di-n-butyl tin maleate, diacetate dibutyl tin, dibutyl tin dioctoate, tin acetate, tin octoate, and various other organometallic compounds such as lead naphthenate, zinc caprylate and cobalt naphthenate. DBTDL is a preferred Lewis acid. Lewis bases that can be used in the practice of the present invention include, but are not limited to, primary, secondary and tertiary amines. These catalysts are typically used in moisture curing applications.

[057] Bronsted acids are chemical species that can lose or donate a hydrogen ion (proton) to a Bronsted base. Bronsted bases are chemical species that can either gain or accept a hydrogen ion from a Bronsted acid. Bronsted acids that can be used in the practice of the present invention include sulfonic acid.

[058] The minimum amount of crosslinking catalyst used in the practice of the present invention is a catalytic amount. Typically, such amount is at least 0.01, preferably at least 0.02 and more preferably at least 0.03 percent by weight (wt%) of the combined weight of ethylene-vinylsilane polymer and catalyst. The only restriction on the maximum amount of crosslinking catalyst in the ethylene polymer is that imposed for reasons of economics and practicality (eg decreasing yield), although typically an overall maximum amount comprises less than 5, preferably less than 3 and more preferably less than 2 weight percent of the combined weight of ethylene polymer and condensation catalyst.

carbon black

[059] In the manufacture of semiconductor compounds, a sufficient amount of conductive charge must be incorporated into the polymer matrix to obtain the desired stable conductivity. In wire and cable applications, the desired conductivity (measured by volumetric resistivity) is generally less than 1000 ohm-cm, preferably less than 500 ohm-cm and more preferably less than 250 ohm-cm. The minimum amount of conductive charge to obtain the target volumetric resistivity is called the percolation threshold. That percolation threshold is the amount of conductive charge below which the volumetric resistivity dramatically increases, and above which the volumetric resistivity is not substantially reduced by adding more conductive charge, and any such increased addition could negatively impact the processability of the compound. For semiconductor compounds for wires and cables, the percolation threshold is in the range of 28-38 percent by weight (% by weight) when using typical conductive carbon blacks such as acetylene black (eg Denka) or Vulcan XC- 500 (Cabot Corp.). With conventional moisture curing, these high levels of carbon black present several challenges including pre-vulcanization (“scorch”), processability issues, and reduced compound flexibility.

[060] To correct these problems and provide an even faster curing system under ambient conditions, for example, 23°C and atmospheric pressure, the preferred conductive charges used in the practice of the present invention are high conductivity carbon blacks, i.e. , carbon blacks that do not require high-level loading, for example, 28 percent or more by weight, based on composition weight, to obtain the percolation threshold, and thus solve these challenges. These and other carbon blacks do not require high loads of conventional carbon blacks and thus do not exacerbate the amounts of moisture brought into the composition or compromise the processability and properties of the product. Representative high conductivity carbon blacks have an average particle size of 50, preferably 40 nanometers (nm) or less, a surface area (BET) of 500 to 1250, preferably 600 to 90 m2/g and an oil absorption ( dibutyl phthalate or DBP) from 200 to 600, preferably from 300 to 500 ml/100g. For example, AKZO Ketjenblack EC300J has a particle size of about 35 nm or less, a surface area (BET) of about 750 to 850 m2/g, and an oil absorption of about 300 to 400 ml/100g.;

[061] High conductivity carbon blacks used in the practice of the present invention can be used alone or in combination with each other. Either alone or in combination with other suitable carbon blacks, they are used in an amount of from 10 to 25%, preferably from 12 to 20% and more preferably from 13 to 18% by weight, based on the total composition of the semiconductor compound. Amounts less than 12 percent by weight can lead to compounds with stable conductivity under thermal aging. Composite using more than 20% by weight can result in materials with increased stiffness (as defined by the M100 tensile modulus). However, smaller or larger amounts can be used if a formulation process or method can be employed to offset smaller or larger amounts than the filler, such as double-pass blending to improve dispersion to the lower limit, and use of polymers increased flexibility base along with addition of suitable plasticizers to provide flexibility for the higher load limit.

Loads and Additives

[062] The composition with which the crosslinked article is prepared, for example, the insulating layer of cable or cable protective jacket, injection molded elastomeric connector, etc., or other manufactured article, for example, sealing, gasket, sole of footwear, etc., can be filled or unfilled. If filled, then the amount of filler/charge present should preferably not exceed an amount that would cause unacceptably large degradation of the electrical and/or mechanical properties of the silane-crosslinked ethylene polymer.

[063] For purposes of the present invention, the fill/filler does not include the conductive carbon blacks described above. If filler is used, this is typically a conductive material, eg metal particulate, or a reinforcing material, eg silica, talc, etc. If present, it is then typically present in an amount of 5 and 25, preferably 10 and 20 percent by weight based on the weight of the composition. Representative fillers include kaolin clay, magnesium hydroxide, silica, calcium carbonate, carbon blacks other than the conductive carbon blacks described above, and elastomeric polymers such as EPDM and EPR. The charge may or may not have flame retardant properties. In one embodiment of the present invention in which the filler is present, the filler is coated with a material that prevents or retards any tendency the filler may have to interfere with the silane curing reaction. Stearic acid is illustrative of this filler coating. The filler and catalyst are selected to avoid any unwanted interactions and reactions and this selection is known in the prior art.

[064] The compositions of the present invention may also contain additives such as, for example, antioxidants (eg, hindered phenols such as, for example, IRGANOXTM 1010, trademark of Ciba Specialty Chemicals), phosphites (eg: IRGAFOSTM 168, trademark from Ciba Specialtt Chemicals), UV stabilizers, thermal stabilizers, cure promoters, adhesion additives, adhesion promoters, light stabilizers (such as hindered amines), plasticizers and/or plasticizer oils (such as dioctylphthalate or soybean oil epoxidized), prevulcanization inhibitors, mold release agents, setting promoters (such as hydrocarbon set promoters), waxes (such as polyethylene waxes), processing aids (such as oils, organic acids, such as acid stearic acid, metallic salts of organic acids), oil expanders (such as paraffinic oil and mineral oil), dyes or pigments as long as they do not interfere with physical or mechanical properties. desired characteristics of the compositions of the present invention. Such additives are known in the state of the art and used in known amounts and in known ways. For example, oils, if present, are typically used in an amount of 5 to 15% by weight, adhesion promoters in an amount of 0.05 to 2% by weight, etc., with the total amount of additives excluding those fillers/fillers, typically not exceeding 20% by weight of the composition.

Formulation/Manufacturing

[065] The formulation of the ethylene polymer functionalized with silane, polyfunctional organopolysiloxane, catalyst, conductive carbon black, and filler and additives, if any, can be performed by standard means known in the prior art. Examples of formulation equipment are internal batch mixers, such as the Banbury or Bolling internal mixer. Alternatively, continuous single screw or twin screw mixers can be used, such as the FarrelTM continuous mixer, a Werner and Pfleiderer twin screw mixer (extruder) or a BussTM continuous kneading extruder. The type of mixer used and its operating conditions affect composition properties such as viscosity, volumetric resistivity, and extruded surface smoothness.

[066] The components of the composition are typically mixed at a temperature and for a period of time sufficient to fully homogenize the mixture, but insufficient to bring the material to gelation. The catalyst is typically added to the ethylene-vinylsilane polymer, but may be added before, along with or after additives, if any. In one embodiment, the components are mixed together in a melt mixing device. The mixture is then molded into the final article. The article formulation and fabrication temperature should be above the melting point of the ethylene-vinylsilane polymer, but below about 250°C.

[067] In one embodiment, the olefinic elastomer, e.g., ENGAGE or AFFINITY polyethylene, available from The Dow Chemical Company, or EXACT polyethylene from Exxon Mobil. it is grafted with vinyl silane in the presence of peroxide in a formulating operation such as a twin screw extruder. Hydroxy-terminated siloxane is then added in-line and melt blended with the grafted polymer. The resulting compound is then recovered and granulated. The granulated compound is mixed with the conductive carbon black in a second formulating run, such as in a BANBURY mixer. Additives and/or fillers can be added at this time. The blend or mixture of granulated compound, carbon black and any additives and/or fillers is then blended with a moisture condensation catalyst, preferably in a standard batch for good homogenization and formed into a finished product such as a molding machine. injection. The article will then crosslink under ambient conditions, that is, without the need for a bain-marie or sauna.

[068] In one embodiment, the process of the present invention comprises the steps of (a) preparing a silane-functionalized polyethylene, grafting a polyethylene with a silane compound under grafting conditions; (b) mixing the silane-functionalized polyethylene with an organopolysiloxane; (c) mixing conductive filler such as high conductivity carbon black and (d) recovering and pelletizing the mixture from (c). Steps (a)-(c) are carried out in-line, that is, in a simple container, thus providing speed and efficiency to the operation. Typically, a step is completed or nearly completed before the start of the next step, although the degree of overlap between two or more steps can vary widely depending on the materials and operating conditions of each step. The addition of crosslinking catalyst is not included in any of these steps. Instead, the crosslinking catalyst is mixed with the pelletized composition at the time the composition is converted into an article, for example, the catalyst is added to the granules at the time they are added to an extruder for processing into wire coating or cable, or at the time the granules are added to a mixer for processing into a molded article.

[069] In some embodiments, either or both the catalyst and the additive are added as a premixed masterbatch. These master batches are commonly formed by dispersing the catalyst and/or additives in an inert plastic resin, eg a low density polyethylene. Master batches are conveniently formed by melt formulation methods.

[070] In one embodiment, one or more of the components are dried prior to formulation, or a mixture of components is dried after formulation, to reduce or eliminate the potential pre-vulcanization problem that can be caused by moisture present or associated with the component. , such as filling. In one embodiment, crosslinkable silane blended polyolefin blends are prepared in the absence of a crosslinking catalyst so that they have extended shelf life and the crosslinking catalyst is added as a final step in preparing a melt-molded article.

Manufactured Items

[071] In one embodiment, the composition of the invention can be applied to a cable in the form of a sheath or insulating layer, in known amounts and by methods also known (for example, with the equipment and methods described in US patents 5,246,783 and 4,144,202). Typically, the composition is prepared in a reactor-extruder equipped with a die for coating cables and after the components of the composition are formulated, the composition is extruded onto the cable as it is drawn through the die. Curing can start in the reactor-extruder.

[072] One of the benefits of the present invention is that the molded article does not require post-molding, such as after demolding or passing through a molding matrix, curing conditions, such as above ambient temperature and/or humidity from an external source such as a water bath or sauna. Although not necessary or preferred, the molded article can be exposed to both elevated temperature and external moisture, and in the case of elevated temperature it is typically between ambient and even below the melting point of the polymer for a period of time. , so that the article achieves a desired degree of crosslinking. The temperature of any post mold cure must be greater than 0°C.

[073] Other articles of manufacture that can be prepared with the polymeric compositions of the present invention include fibers, tapes, sheets, straps, tubes, cables, weather protectors, seals, gaskets, foams, footwear and ventilation means. These items can be manufactured using known equipment and techniques.

[074] The invention is described more comprehensively through the examples described below. Unless otherwise noted, all parts and percentages are by weight. Specific Embodiments Comparative Examples CE-1, CE-2 and CE-3

Nordel IP 3430 EPDM: ENB 0,7%, Viscosidade Mooney 27,cristalinidade <1%, teor de etileno 42%, da The Dow Chemical Company. Nordel IP 3722P EPDM: ENB 0,5%, Viscosidade Mooney 18, cristalinidade 15%, teor de etileno 71%, da The Dow Chemical Company. AKZO Ketjenblack Black EC-300J tem um tamanho de partícula de 35 nm ou menor, uma área superficial (BET) de 750 a 850 m2/g, absorção de iodo de 740-840 ml 100 gramas, e uma absorção de óleo (DBP) de 300 a 400 ml/100g. Negro de fumo Cabot VXC805, uma absorção de iodo de 370 a 470 ml/100g. Negro de fumo XC500, absorção de óleo (DBP) de 140 a 155 ml/100 g, e uma absorção de iodo de 70 a 80 ml/100g. Óleo SUNPAR 2280, óleo de processo parafínico da R.E.Carroll Corp. Óxido de zinco, estabilizante em compostos de borracha e elastoméricos reticuláveis tais como os fornecidos pela Stuktol Company of America. Peróxido Perkadox 14S FL, um di(ter- butilperoxiisopropil)benzeno, flocos de peróxido da Akzo Nobel Polymer Chemicals. Resistência à tração, alongamento na ruptura, M100: ASTM D638. Shore A: ASTM D2240 Resistência ao rasgo (matriz B): ASTM D624 Resistividade volumétrica é medida em corpos de prova coletados de placas com 8 x 2 x 0,75” preparadas através de moldagem por compressão do composto sob condições termoplásticas. Os corpos de prova são resfriados à temperatura ambiente e removidos do molde. Os corpos de prova são revestidos com uma tinta condutora, e então condutores de cobre chatos (16 AWG) são envolvidos em torno de cada placa em cada extremidade da placa para que os condutores fiquem 2” afastados um do outro e cada qual tenha cerca de 1” desde a extremidade da placa. O fio condutor revestido é prensado para obter bom contato com a tinta condutora, e então o corpo de prova envolvido com fio é colocado em um forno com aparelho para monitorar a resistividade volumétrica à temperatura especificada. A Fluência a Quente é medida como alongamento percentual sob carga de 20N/mm2 em um forno a 150°C por 15 minutos. Um padrão comum para reticulação adequada é um alongamento igual ou menor que (<) 100%. As medições são obtidas em amostras em triplicata. MDR: A Cinética de Reticulação é avaliada utilizando-se um Reômetro de Matriz Móvel (MDR), ajustado a 100 ciclos por minutos, e então um arco de 0,5 graus. Os dados de torque estão correlacionados com o grau de reticulação, sendo obtidos como função do tempo de cura. A câmara MDR é ajustada a uma temperatura de 177°C. O valor mais baixo de torque (ML, N-m (em pol-lb)) é reportado como indicação de formação de viscosidade, ou seja, facilidade de processamento de cada uma das composições.[075] The following examples use standard EPDM compositions based on peroxide that are vulcanized at high temperature. These represent the current practice of curing in a hot mold (here simulated by a press curing step held at 175°C for 10 minutes). Table 1

Nordel IP 3430 EPDM: ENB 0.7%, Mooney Viscosity 27, Crystallinity <1%, Ethylene Content 42%, from The Dow Chemical Company. Nordel IP 3722P EPDM: 0.5% ENB, Mooney 18 Viscosity, 15% crystallinity, 71% ethylene content, from The Dow Chemical Company. AKZO Ketjenblack Black EC-300J has a particle size of 35 nm or smaller, a surface area (BET) of 750 to 850 m2/g, an iodine absorption of 740-840 ml 100 grams, and an oil absorption (DBP) from 300 to 400 ml/100g. Cabot VXC805 carbon black, an iodine absorption of 370 to 470 ml/100g. XC500 carbon black, oil absorption (DBP) from 140 to 155 ml/100 g, and an iodine absorption from 70 to 80 ml/100g. SUNPAR 2280 Oil, paraffinic process oil from RECarroll Corp. Zinc oxide, stabilizer in crosslinkable rubber and elastomeric compounds such as those supplied by the Stuktol Company of America. Perkadox 14S FL peroxide, a di(tert-butylperoxyisopropyl)benzene, peroxide flakes from Akzo Nobel Polymer Chemicals. Tensile Strength, Elongation at Break, M100: ASTM D638. Shore A: ASTM D2240 Tear resistance (matrix B): ASTM D624 Volumetric resistivity is measured on specimens collected from 8 x 2 x 0.75” plates prepared by compression molding the compound under thermoplastic conditions. The specimens are cooled to room temperature and removed from the mold. The specimens are coated with a conductive paint, and then flat copper conductors (16 AWG) are wrapped around each plate at each end of the plate so that the conductors are 2" apart from each other and each is approximately 1” from the edge of the plate. The coated conductive wire is pressed to obtain good contact with the conductive ink, and then the wire-wrapped specimen is placed in an oven fitted with an apparatus to monitor the volumetric resistivity at the specified temperature. Hot creep is measured as percent elongation under a load of 20N/mm2 in an oven at 150°C for 15 minutes. A common pattern for proper crosslinking is an elongation equal to or less than (<) 100%. Measurements are taken on triplicate samples. MDR: Crosslink Kinetics is evaluated using a Moving Matrix Rheometer (MDR), set at 100 cycles per minute, and then a 0.5 degree arc. Torque data are correlated with the degree of crosslinking, being obtained as a function of cure time. The MDR camera is set at a temperature of 177°C. The lowest torque value (ML, Nm (in in-lb)) is reported as an indication of viscosity build-up, that is, ease of processing for each of the compositions.

Inventive Examples IE1 - IE5 and Comparative Example 4

[076] Examples IE1 to IE3 below represent the invention in which a silane grafted olefinic elastomer containing 5% hydroxyl terminated polydimethylsiloxane (OH-PDMS) is prepared in a first step in a twin screw extruder, and then combined into a batch mixer with high conductivity carbon black, then a standard batch of dibutyl tin catalyst is added during the formulation/mixing step. The composite is compression molded in a press at 150°C, cooled and demolded. Plates are cured for 3 days under ambient conditions.

[077] The examples show excellent curing and mechanical properties, and using high conductivity carbon blacks (AKZO Ketjenblack EC300 or Cabot VXC805) gives excellent electrical conductivity at low filler load which results in the desired flexible material (shown in M100 values). The examples also show the level of charge required for the desired conductivity. For example, at 12% load, the conductivity is not stable as shown by peak volumetric resistivity (VR) increases during the aging period. Those skilled in the art also know that such compounds require a post-formulation drying step to remove excess moisture caused by carbon black. These examples illustrate the invention for a semiconductor compound that can be molded into thermoplastic form, and then cured to ambient conditions, thus eliminating the in-mold vulcanization step.

DBTDL é dilaurato de dibutil estanho, tal como o FASCAT 4202 da Arkema, Inc.[078] Comparative Example 4 illustrates the need to properly choose the conductive charge: Although a much larger charge is needed (37% by weight), the VR is not as good as when using high conductivity carbon blacks, although also resulting in a much stiffer compound, as shown by the M100 value, thus compromising flexibility as well as generating a more viscous system, which could cause processing difficulties. Table 2

DBTDL is dibutyl tin dilaurate, such as FASCAT 4202 from Arkema, Inc.

Claims (10)

1. Peroxide-free crosslinkable semiconductor thermoplastic composition, having a stable volumetric resistivity of less than 1000 ohm-cm at 90°C, characterized in that it comprises, based on the weight of the composition: A. from 60-90% by weight of polyethylene silane functionalized; B. 0.5-20% by weight of organopolysiloxane containing two or more functional end groups; and C. from 10-20% by weight of carbon black having an average particle size of 50 nm or less, a surface area (BET) of 700-1250 m 2 /g and an oil absorption (DBP) of 300-500 ml/100g; and D. from 0.05 - 0.2% by weight of crosslinking catalyst. 2. Composition according to claim 1, characterized in that it has a stable volumetric resistivity of less than 500 ohm-cm at 90°C. 3. Composition according to claim 1, characterized in that the silane-functionalized polyethylene is a silane-functionalized ethylene/α-olefin interpolymer having an α-olefin content of 15 to 50% by weight, based on the interpolymer weight. 4. Composition according to claim 1, characterized in that the silane functionality of the polyethylene comprises at least 0.5% by weight of the total weight of the polyethylene. 5. Composition according to claim 1, characterized in that the organopolysiloxane has the formula R2SiO where each R is independently selected from a group consisting of alkyl radicals comprising from one to 12 carbon atoms, alkenyl radicals comprising from two to 12 carbon atoms, aryl, and fluorine-substituted alkyl radicals comprising from one to 12 carbon atoms. 6. Process for preparing a crosslinked semiconductor thermoplastic article, from the crosslinkable thermoplastic composition, having a stable volumetric resistivity of less than 1000 ohm-cm at 90°C, as defined in claim 1, characterized in that it comprises the steps of: A combining a silane-functionalized polyethylene with an organopolysiloxane containing two or more functional end groups to form a crosslinkable compound; B. combining, under ambient conditions, (1) the crosslinkable compound of (A) with (2) carbon black having an average particle size of 50 nm or less, a surface area (BET) of 700-1250 m2/g , and an oil absorption (DBP) of 300-500 ml/100g, to form a first mixture comprising from 80-90% by weight of the crosslinkable compound of (A) and 10-20% by weight of the carbon black, with based on the weight of the first mixture; C. combining the first mixture with 0.05-0.2% by weight of a crosslinking catalyst to form a homogeneous second mixture; D. molding the second mixture under non-crosslinking conditions into a crosslinkable semiconductor thermoplastic article; and E. subjecting the molded crosslinkable semiconductor thermoplastic article to crosslinking conditions. 7. Process according to claim 6, characterized in that it comprises the step of pelletizing the crosslinkable compound of (A) before mixing it with the organopolysiloxane. 8. Process according to claim 6, characterized in that the catalyst is added as a pre-mixed standard batch. 9. In-line process for preparing a cross-linkable composition, the cross-linkable composition being obtained without the addition of the cross-linking catalyst defined in claim 1 and the in-line process being characterized by the fact that it comprises the steps of (a) preparing a functionalized polyethylene with silane grafting a polyethylene with a silane compound under grafting conditions; (b) mixing the silane-functionalized polyethylene with an organopolysiloxane; (c) blending a high conductivity carbon black having an average particle size of 50 nm or less, a surface area (BET) of 700-1250 m2/g and an oil absorption (DBP) of 300-500 ml/100g , with the mixture formed in step (b), and (d) recovering and pelletizing the mixture formed in step (c). 10. Granule, characterized in that it is prepared according to the process defined in any one of claims 6 or 9 and comprising: A. from 60-90% by weight of silane-functionalized polyethylene; B. 0.5-20% by weight of organopolysiloxane containing two or more functional end groups; C. of 10-20% by weight of high conductivity carbon black and conductive carbon black having an average particle size of 50 nm or less, a surface area (BET) of 700-1250 m2/g and an absorption of 300-500 ml/100g oil (DBP).